2. Logic Array Blocks and Adaptive Logic
Modules in Stratix IV Devices
February 2011
SIV51002-3.1
SIV51002-3.1
This chapter describes the features of the logic array blocks (LABs) in the Stratix® IV
core fabric. LABs are made up of adaptive logic modules (ALMs) that you can
configure to implement logic functions, arithmetic functions, and register functions.
LABs and ALMs are the basic building blocks of the Stratix IV device. Use these to
configure logic, arithmetic, and register functions. The ALM provides advanced
features with efficient logic usage and is completely backward-compatible.
This chapter contains the following sections:
■
“Logic Array Blocks”
■
“Adaptive Logic Modules” on page 2–5
Logic Array Blocks
Each LAB consists of ten ALMs, various carry chains, shared arithmetic chains, LAB
control signals, local interconnect, and register chain connection lines. The local
interconnect transfers signals between ALMs in the same LAB. The direct link
interconnect allows the LAB to drive into the local interconnect of its left and right
neighbors. Register chain connections transfer the output of the ALM register to the
adjacent ALM register in the LAB. The Quartus® II Compiler places associated logic in
the LAB or adjacent LABs, allowing the use of local, shared arithmetic chain, and
register chain connections for performance and area efficiency.
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Chapter 2: Logic Array Blocks and Adaptive Logic Modules in Stratix IV Devices
Logic Array Blocks
Figure 2–1 shows the Stratix IV LAB structure and interconnects.
Figure 2–1. Stratix IV LAB Structure and Interconnects
C4
C12
Row Interconnects of
Variable Speed & Length
R20
R4
ALMs
Direct link
interconnect from
adjacent block
Direct link
interconnect from
adjacent block
Direct link
interconnect to
adjacent block
Direct link
interconnect to
adjacent block
Local Interconnect
LAB
MLAB
Local Interconnect is Driven
from Either Side by Columns & LABs,
& from Above by Rows
Column Interconnects of
Variable Speed & Length
The LAB of the Stratix IV device has a derivative called memory LAB (MLAB), which
adds look-up table (LUT)-based SRAM capability to the LAB, as shown in Figure 2–2.
The MLAB supports a maximum of 640 bits of simple dual-port static random access
memory (SRAM). You can configure each ALM in an MLAB as either a 64 × 1 or a
32 × 2 block, resulting in a configuration of either a 64 × 10 or a 32 × 20 simple
dual-port SRAM block. MLAB and LAB blocks always coexist as pairs in all Stratix IV
families. MLAB is a superset of the LAB and includes all LAB features.
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Logic Array Blocks
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f The MLAB is described in detail in the TriMatrix Embedded Memory Blocks in Stratix IV
Devices chapter.
Figure 2–2. Stratix IV LAB and MLAB Structure
LUT-based-64 x 1
Simple dual-port SRAM
(1)
ALM
LUT-based-64 x 1
Simple dual-port SRAM
(1)
LUT-based-64 x 1
Simple dual-port SRAM
(1)
LUT-based-64 x 1
Simple dual-port SRAM
(1)
LUT-based-64 x 1
Simple dual-port SRAM
(1)
ALM
LAB Control Block
(1)
ALM
LUT-based-64 x 1
Simple dual-port SRAM
(1)
LUT-based-64 x 1
Simple dual-port SRAM
(1)
LUT-based-64 x 1
Simple dual-port SRAM
(1)
LUT-based-64 x 1
Simple dual-port SRAM
(1)
MLAB
ALM
ALM
LAB Control Block
LUT-based-64 x 1
Simple dual-port SRAM
ALM
ALM
ALM
ALM
ALM
LAB
Note to Figure 2–2:
(1) You can use the MLAB ALM as a regular LAB ALM or configure it as a dual-port SRAM, as shown.
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Logic Array Blocks
LAB Interconnects
The LAB local interconnect can drive ALMs in the same LAB. It is driven by column
and row interconnects and ALM outputs in the same LAB. Neighboring
LABs/MLABs, M9K RAM blocks, M144K blocks, or digital signal processing (DSP)
blocks from the left or right can also drive the LAB’s local interconnect through the
direct link connection. The direct link connection feature minimizes the use of row
and column interconnects, providing higher performance and flexibility. Each LAB
can drive 30 ALMs through fast-local and direct-link interconnects.
Figure 2–3 shows the direct-link connection.
Figure 2–3. Direct-Link Connection
Direct-link interconnect from the
left LAB, TriMatrix memory
block, DSP block, or IOE output
Direct-link interconnect from the
right LAB, TriMatrix memory
block, DSP block, or IOE output
ALMs
ALMs
Direct-link
interconnect
to right
Direct-link
interconnect
to left
Local
Interconnect
MLAB
LAB
LAB Control Signals
Each LAB contains dedicated logic for driving control signals to its ALMs. Control
signals include three clocks, three clock enables, two asynchronous clears, a
synchronous clear, and synchronous load control signals. This gives a maximum of 10
control signals at a time. Although you generally use synchronous-load and clear
signals when implementing counters, you can also use them with other functions.
Each LAB has two unique clock sources and three clock enable signals, as shown in
Figure 2–4. The LAB control block can generate up to three clocks using two clock
sources and three clock enable signals. Each LAB’s clock and clock enable signals are
linked. For example, any ALM in a particular LAB using the labclk1 signal also uses
the labclkena1 signal. If the LAB uses both the rising and falling edges of a clock, it
also uses two LAB-wide clock signals. De-asserting the clock enable signal turns off
the corresponding LAB-wide clock.
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Adaptive Logic Modules
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The LAB row clocks [5..0] and LAB local interconnects generate the LAB-wide control
signals. The MultiTrack interconnect’s inherent low skew allows clock and control
signal distribution in addition to data.
Figure 2–4. LAB-Wide Control Signals
There are two unique
clock signals per LAB.
6
Dedicated Row LAB Clocks
6
6
Local Interconnect
Local Interconnect
Local Interconnect
Local Interconnect
Local Interconnect
Local Interconnect
labclk0
labclk1
labclkena0
or asyncload
or labpreset
labclk2
labclkena1
labclkena2
labclr1
syncload
labclr0
synclr
Adaptive Logic Modules
The ALM is the basic building block of logic in the Stratix IV architecture. It provides
advanced features with efficient logic usage. Each ALM contains a variety of
LUT-based resources that can be divided between two combinational adaptive LUTs
(ALUTs) and two registers. With up to eight inputs for the two combinational ALUTs,
one ALM can implement various combinations of two functions. This adaptability
allows an ALM to be completely backward-compatible with four-input LUT
architectures. One ALM can also implement any function with up to six inputs and
certain seven-input functions.
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Adaptive Logic Modules
In addition to the adaptive LUT-based resources, each ALM contains two
programmable registers, two dedicated full adders, a carry chain, a shared arithmetic
chain, and a register chain. Through these dedicated resources, an ALM can
efficiently implement various arithmetic functions and shift registers. Each ALM
drives all types of interconnects: local, row, column, carry chain, shared arithmetic
chain, register chain, and direct link. Figure 2–5 shows a high-level block diagram of
the Stratix IV ALM.
Figure 2–5. High-Level Block Diagram of the Stratix IV ALM
shared_arith_in
carry_in
Combinational/Memory ALUT0
reg_chain_in
labclk
To general or
local routing
dataf0
datae0
6-Input LUT
adder0
D
Q
dataa
To general or
local routing
reg0
datab
datac
datad
datae1
adder1
D
Q
6-Input LUT
To general or
local routing
reg1
dataf1
To general or
local routing
Combinational/Memory ALUT1
reg_chain_out
shared_arith_out
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Adaptive Logic Modules
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Figure 2–6 shows a detailed view of all the connections in an ALM.
Figure 2–6. Stratix IV ALM Connection Details
syncload
aclr[1:0]
shared_arith_in
carry_in
clk[2:0]
sclr
reg_chain_in
dataf0
datae0
dataa
datab
GND
4-INPUT
LUT
datac0
+
CLR
D
Q
3-INPUT
LUT
local
interconnect
row, column
direct link routing
row, column
direct link routing
3-INPUT
LUT
4-INPUT
LUT
datac1
+
CLR
D
Q
3-INPUT
LUT
local
interconnect
row, column
direct link routing
row, column
direct link routing
3-INPUT
LUT
VCC
datae1
dataf1
shared_arith_out
carry_out
reg_chain_out
One ALM contains two programmable registers. Each register has data, clock, clock
enable, synchronous and asynchronous clear, and synchronous load and clear inputs.
Global signals, general-purpose I/O pins, or any internal logic can drive the register’s
clock and clear-control signals. Either general-purpose I/O pins or internal logic can
drive the clock enable. For combinational functions, the register is bypassed and the
output of the LUT drives directly to the outputs of an ALM.
Each ALM has two sets of outputs that drive the local, row, and column routing
resources. The LUT, adder, or register outputs can drive these output drivers (refer to
Figure 2–6). For each set of output drivers, two ALM outputs can drive column, row,
or direct-link routing connections. One of these ALM outputs can also drive local
interconnect resources. This allows the LUT or adder to drive one output while the
register drives another output.
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Adaptive Logic Modules
This feature, called register packing, improves device utilization because the device
can use the register and the combinational logic for unrelated functions. Another
special packing mode allows the register output to feed back into the LUT of the same
ALM so that the register is packed with its own fan-out LUT. This provides another
mechanism for improved fitting. The ALM can also drive out registered and
unregistered versions of the LUT or adder output.
ALM Operating Modes
The Stratix IV ALM operates in one of the following modes:
■
Normal
■
Extended LUT
■
Arithmetic
■
Shared Arithmetic
■
LUT-Register
Each mode uses ALM resources differently. In each mode, eleven available inputs to
an ALM—the eight data inputs from the LAB local interconnect, carry-in from the
previous ALM or LAB, the shared arithmetic chain connection from the previous
ALM or LAB, and the register chain connection—are directed to different destinations
to implement the desired logic function. LAB-wide signals provide clock,
asynchronous clear, synchronous clear, synchronous load, and clock enable control
for the register. These LAB-wide signals are available in all ALM modes.
For more information about the LAB-wide control signals, refer to “LAB Control
Signals” on page 2–4.
The Quartus II software and supported third-party synthesis tools, in conjunction
with parameterized functions such as the library of parameterized modules (LPM)
functions, automatically choose the appropriate mode for common functions such as
counters, adders, subtractors, and arithmetic functions.
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Adaptive Logic Modules
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Normal Mode
Normal mode is suitable for general logic applications and combinational functions.
In this mode, up to eight data inputs from the LAB local interconnect are inputs to the
combinational logic. Normal mode allows two functions to be implemented in one
Stratix IV ALM, or a single function of up to six inputs. The ALM can support certain
combinations of completely independent functions and various combinations of
functions that have common inputs.
Figure 2–7 shows the supported LUT combinations in normal mode.
Figure 2–7. ALM in Normal Mode (Note 1)
dataf0
datae0
datac
dataa
4-Input
LUT
combout0
datab
datad
datae1
dataf1
4-Input
LUT
combout1
dataf0
datae0
datac
dataa
datab
5-Input
LUT
combout0
datad
datae1
dataf1
3-Input
LUT
dataf0
datae0
datac
dataa
datab
5-Input
LUT
4-Input
LUT
datad
datae1
dataf1
dataf0
datae0
datac
dataa
datab
5-Input
LUT
combout0
5-Input
LUT
combout1
dataf0
datae0
dataa
datab
datac
datad
6-Input
LUT
combout0
dataf0
datae0
dataa
datab
datac
datad
6-Input
LUT
combout0
6-Input
LUT
combout1
datad
datae1
dataf1
combout1
combout0
combout1
datae1
dataf1
Note to Figure 2–7:
(1) Combinations of functions with fewer inputs than those shown are also supported. For example, combinations of functions with the following
number of inputs are supported: 4 and 3, 3 and 3, 3 and 2, and 5 and 2.
Normal mode provides complete backward-compatibility with four-input LUT
architectures.
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Adaptive Logic Modules
For the packing of 2 five-input functions into one ALM, the functions must have at
least two common inputs. The common inputs are dataa and datab. The combination
of a four-input function with a five-input function requires one common input (either
dataa or datab).
In the case of implementing 2 six-input functions in one ALM, four inputs must be
shared and the combinational function must be the same. In a sparsely used device,
functions that could be placed in one ALM may be implemented in separate ALMs by
the Quartus II software to achieve the best possible performance. As a device begins
to fill up, the Quartus II software automatically uses the full potential of the Stratix IV
ALM. The Quartus II Compiler automatically searches for functions using common
inputs or completely independent functions to be placed in one ALM to make efficient
use of device resources. In addition, you can manually control resource usage by
setting location assignments.
You can implement any six-input function using inputs dataa, datab, datac, datad,
and either datae0 and dataf0 or datae1 and dataf1. If you use datae0 and dataf0, the
output is driven to register0, and/or register0 is bypassed and the data drives out
to the interconnect using the top set of output drivers (refer to Figure 2–8). If you use
datae1 and dataf1, the output either drives to register1 or bypasses register1 and
drives to the interconnect using the bottom set of output drivers. The Quartus II
Compiler automatically selects the inputs to the LUT. ALMs in normal mode support
register packing.
Figure 2–8. Input Function in Normal Mode (Note 1)
dataf0
datae0
dataa
datab
datac
datad
To general or
local routing
6-Input
LUT
D
Q
To general or
local routing
reg0
datae1
dataf1
(2)
D
labclk
Q
To general or
local routing
reg1
These inputs are available for register packing.
Notes to Figure 2–8:
(1) If you use datae1 and dataf1 as inputs to a six-input function, datae0 and dataf0 are available for register packing.
(2) The dataf1 input is available for register packing only if the six-input function is unregistered.
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Adaptive Logic Modules
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Extended LUT Mode
Use extended LUT mode to implement a specific set of seven-input functions. The set
must be a 2-to-1 multiplexer fed by two arbitrary five-input functions sharing four
inputs. Figure 2–9 shows the template of supported seven-input functions using
extended LUT mode. In this mode, if the seven-input function is unregistered, the
unused eighth input is available for register packing.
Functions that fit into the template shown in Figure 2–9 occur naturally in designs.
These functions often appear in designs as “if-else” statements in Verilog HDL or
VHDL code.
Figure 2–9. Template for Supported Seven-Input Functions in Extended LUT Mode
datae0
datac
dataa
datab
datad
dataf0
5-Input
LUT
To general or
local routing
combout0
D
5-Input
LUT
Q
To general or
local routing
reg0
datae1
dataf1
(1)
This input is available
for register packing.
Note to Figure 2–9:
(1) If the seven-input function is unregistered, the unused eighth input is available for register packing. The second register, reg1, is
not available.
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Adaptive Logic Modules
Arithmetic Mode
Arithmetic mode is ideal for implementing adders, counters, accumulators, wide
parity functions, and comparators. The ALM in arithmetic mode uses two sets of
2 four-input LUTs along with two dedicated full adders. The dedicated adders allow
the LUTs to be available to perform pre-adder logic; therefore, each adder can add the
output of 2 four-input functions.
The four LUTs share dataa and datab inputs. As shown in Figure 2–10, the carry-in
signal feeds to adder0 and the carry-out from adder0 feeds to the carry-in of adder1.
The carry-out from adder1 drives to adder0 of the next ALM in the LAB. ALMs in
arithmetic mode can drive out registered and/or unregistered versions of the adder
outputs.
Figure 2–10. ALM in Arithmetic Mode
carry_in
datae0
adder0
4-Input
LUT
To general or
local routing
D
dataf0
datac
datab
dataa
datad
datae1
Q
To general or
local routing
reg0
4-Input
LUT
adder1
4-Input
LUT
To general or
local routing
D
4-Input
LUT
Q
To general or
local routing
reg1
dataf1
carry_out
While operating in arithmetic mode, the ALM can support simultaneous use of the
adder’s carry output along with combinational logic outputs. In this operation, adder
output is ignored. Using the adder with combinational logic output provides resource
savings of up to 50% for functions that can use this ability.
Arithmetic mode also offers clock enable, counter enable, synchronous up/down
control, add/subtract control, synchronous clear, and synchronous load. The LAB
local interconnect data inputs generate the clock enable, counter enable, synchronous
up/down, and add/subtract control signals. These control signals are good
candidates for the inputs that are shared between the four LUTs in the ALM. The
synchronous clear and synchronous load options are LAB-wide signals that affect all
registers in the LAB. These signals can also be individually disabled or enabled per
register. The Quartus II software automatically places any registers that are not used
by the counter into other LABs.
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Adaptive Logic Modules
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Carry Chain
The carry chain provides a fast carry function between the dedicated adders in
arithmetic or shared-arithmetic mode. The two-bit carry select feature in Stratix IV
devices halves the propagation delay of carry chains within the ALM. Carry chains
can begin in either the first ALM or the fifth ALM in the LAB. The final carry-out
signal is routed to the ALM, where it is fed to local, row, or column interconnects.
The Quartus II Compiler automatically creates carry-chain logic during design
processing, or you can create it manually during design entry. Parameterized
functions such as LPM functions automatically take advantage of carry chains for the
appropriate functions.
The Quartus II Compiler creates carry chains longer than 20 (10 ALMs in arithmetic or
shared arithmetic mode) by linking LABs together automatically. For enhanced
fitting, a long carry chain runs vertically, allowing fast horizontal connections to
TriMatrix memory and DSP blocks. A carry chain can continue as far as a full column.
To avoid routing congestion in one small area of the device when a high fan-in
arithmetic function is implemented, the LAB can support carry chains that only use
either the top half or bottom half of the LAB before connecting to the next LAB. This
leaves the other half of the ALMs in the LAB available for implementing narrower
fan-in functions in normal mode. Carry chains that use the top five ALMs in the first
LAB carry into the top half of the ALMs in the next LAB within the column. Carry
chains that use the bottom five ALMs in the first LAB carry into the bottom half of the
ALMs in the next LAB within the column. In every alternate LAB column, the top half
can be bypassed; in the other MLAB columns, the bottom half can be bypassed.
For more information about carry-chain interconnects, refer to “ALM Interconnects”
on page 2–18.
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Adaptive Logic Modules
Shared Arithmetic Mode
In shared arithmetic mode, the ALM can implement a three-input add within the
ALM. In this mode, the ALM is configured with 4 four-input LUTs. Each LUT either
computes the sum of three inputs or the carry of three inputs. The output of the carry
computation is fed to the next adder (either to adder1 in the same ALM or to adder0 of
the next ALM in the LAB) using a dedicated connection called the shared arithmetic
chain. This shared arithmetic chain can significantly improve the performance of an
adder tree by reducing the number of summation stages required to implement an
adder tree. Figure 2–11 shows the ALM using this feature.
Figure 2–11. ALM in Shared Arithmetic Mode
shared_arith_in
carry_in
labclk
4-Input
LUT
To general or
local routing
D
datae0
datac
datab
dataa
datad
datae1
Q
To general or
local routing
reg0
4-Input
LUT
4-Input
LUT
To general or
local routing
D
4-Input
LUT
Q
To general or
local routing
reg1
carry_out
shared_arith_out
You can find adder trees in many different applications. For example, the summation
of the partial products in a logic-based multiplier can be implemented in a tree
structure. Another example is a correlator function that can use a large adder tree to
sum filtered data samples in a given time frame to recover or de-spread data that was
transmitted using spread-spectrum technology.
Shared Arithmetic Chain
The shared arithmetic chain available in enhanced arithmetic mode allows the ALM
to implement a three-input add. This significantly reduces the resources necessary to
implement large adder trees or correlator functions.
Shared arithmetic chains can begin in either the first or sixth ALM in the LAB. The
Quartus II Compiler creates shared arithmetic chains longer than 20 (10 ALMs in
arithmetic or shared arithmetic mode) by linking LABs together automatically. For
enhanced fitting, a long shared arithmetic chain runs vertically, allowing fast
horizontal connections to the TriMatrix memory and DSP blocks. A shared arithmetic
chain can continue as far as a full column.
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Similar to the carry chains, the top and bottom halves of shared arithmetic chains in
alternate LAB columns can be bypassed. This capability allows the shared arithmetic
chain to cascade through half of the ALMs in an LAB while leaving the other half
available for narrower fan-in functionality. Every other LAB column is top-half
by-passable, while the other LAB columns are bottom-half by-passable.
For more information about the shared arithmetic chain interconnect, refer to “ALM
Interconnects” on page 2–18.
LUT-Register Mode
LUT-register mode allows third-register capability within an ALM. Two internal
feedback loops allow combinational ALUT1 to implement the master latch and
combinational ALUT0 to implement the slave latch needed for the third register. The
LUT register shares its clock, clock enable, and asynchronous clear sources with the
top dedicated register. Figure 2–12 shows the register constructed using two
combinational blocks within the ALM.
Figure 2–12. LUT Register from Two Combinational Blocks
sumout
clk
aclr
LUT regout
4-input
LUT
combout
5-input
LUT
combout
sumout
datain(datac)
sclr
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Figure 2–13 shows the ALM in LUT-register mode.
Figure 2–13. ALM in LUT-Register Mode with Three-Register Capability
clk [2:0]
aclr [1:0]
DC1
reg_chain_in
datain
lelocal 0
aclr
aclr
sclr
regout
datain
latchout
sdata
leout 0 a
regout
leout 0 b
E0
F1
lelocal 1
aclr
datain
E1
sdata
F0
leout 1 a
regout
leout 1 b
reg_chain_out
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Register Chain
In addition to general routing outputs, ALMs in the LAB have register-chain outputs.
Register-chain routing allows registers in the same LAB to be cascaded together. The
register-chain interconnect allows the LAB to use LUTs for a single combinational
function and the registers to be used for an unrelated shift-register implementation.
These resources speed up connections between ALMs while saving local interconnect
resources (refer to Figure 2–14). The Quartus II Compiler automatically takes
advantage of these resources to improve utilization and performance.
Figure 2–14. Register Chain within the LAB (Note 1)
From previous ALM
within the LAB
reg_chain_in
labclk
To general or
local routing
adder0
D
Q
To general or
local routing
reg0
Combinational
Logic
adder1
D
Q
To general or
local routing
reg1
To general or
local routing
To general or
local routing
adder0
D
Q
To general or
local routing
reg0
Combinational
Logic
adder1
D
Q
To general or
local routing
reg1
To general or
local routing
reg_chain_out
To next ALM
within the LAB
Note to Figure 2–14:
(1) You can use the combinational or adder logic to implement an unrelated, un-registered function.
For more information about the register chain interconnect, refer to “ALM
Interconnects” on page 2–18.
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ALM Interconnects
There are three dedicated paths between the ALMs—register cascade, carry chain,
and shared arithmetic chain. Stratix IV devices include an enhanced interconnect
structure in LABs for routing shared arithmetic chains and carry chains for efficient
arithmetic functions. The register chain connection allows the register output of one
ALM to connect directly to the register input of the next ALM in the LAB for fast shift
registers. These ALM-to-ALM connections bypass the local interconnect. The
Quartus II Compiler automatically takes advantage of these resources to improve
utilization and performance. Figure 2–15 shows the shared arithmetic chain, carry
chain, and register chain interconnects.
Figure 2–15. Shared Arithmetic Chain, Carry Chain, and Register Chain Interconnects
Local interconnect
routing among ALMs
in the LAB
Carry chain & shared
arithmetic chain
routing to adjacent ALM
ALM 1
Register chain
routing to adjacent
ALM's register input
ALM 2
Local
interconnect
ALM 3
ALM 4
ALM 5
ALM 6
ALM 7
ALM 8
ALM 9
ALM 10
Clear and Preset Logic Control
LAB-wide signals control the logic for the register ’s clear signal. The ALM directly
supports an asynchronous clear function. You can achieve the register preset through
the Quartus II software’s NOT-gate push-back logic option. Each LAB supports up to
two clears.
Stratix IV devices provide a device-wide reset pin (DEV_CLRn) that resets all the
registers in the device. An option set before compilation in the Quartus II software
controls this pin. This device-wide reset overrides all other control signals.
Stratix IV Device Handbook Volume 1
February 2011
Altera Corporation
Chapter 2: Logic Array Blocks and Adaptive Logic Modules in Stratix IV Devices
Document Revision History
2–19
LAB Power Management Techniques
The following techniques are used to manage static and dynamic power consumption
within the LAB:
■
To save AC power, the Quartus II software forces all adder inputs low when ALM
adders are not in use.
■
Stratix IV LABs operate in high-performance mode or low-power mode. The
Quartus II software automatically chooses the appropriate mode for the LAB,
based on the design, to optimize speed versus leakage trade-offs.
■
Clocks represent a significant portion of dynamic power consumption due to their
high switching activity and long paths. The LAB clock that distributes a clock
signal to registers within an LAB is a significant contributor to overall clock power
consumption. Each LAB’s clock and clock enable signal are linked. For example, a
combinational ALUT or register in a particular LAB using the labclk1 signal also
uses the labclkena1 signal. To disable LAB-wide clock power consumption
without disabling the entire clock tree, use LAB-wide clock enable to gate the
LAB-wide clock. The Quartus II software automatically promotes register-level
clock enable signals to the LAB-level. All registers within the LAB that share a
common clock and clock enable are controlled by a shared, gated clock. To take
advantage of these clock enables, use a clock-enable construct in your HDL code
for the registered logic.
f For more information about implementing static and dynamic power consumption
within the LAB, refer to the Power Optimization chapter in volume 2 of the Quartus II
Handbook.
Document Revision History
Table 2–1 lists the revision history for this chapter.
Table 2–1. Document Revision History
Date
Version
February 2011
November 2009
June 2009
3.1
3.0
2.2
March 2009
2.1
November 2008
2.0
May 2008
February 2011
1.0
Altera Corporation
Changes
■
Updated Figure 2–6.
■
Applied new template.
■
Minor text edits.
■
Updated graphics.
■
Minor text edits.
■
Removed the Conclusion section.
■
Added introductory sentences to improve search ability.
■
Minor text edits.
Removed “Referenced Documents” section.
■
Updated Figure 2–6.
■
Made minor editorial changes.
Initial release.
Stratix IV Device Handbook Volume 1
2–20
Stratix IV Device Handbook Volume 1
Chapter 2: Logic Array Blocks and Adaptive Logic Modules in Stratix IV Devices
Document Revision History
February 2011
Altera Corporation